Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-26T13:23:08Z No. of bitstreams: 1 marianagenymoreira.pdf: 8374988 bytes, checksum: 38a7b2c61f3df104e6c9f034df1386ae (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-26T13:53:43Z (GMT) No. of bitstreams: 1 marianagenymoreira.pdf: 8374988 bytes, checksum: 38a7b2c61f3df104e6c9f034df1386ae (MD5) / Made available in DSpace on 2017-04-26T13:53:43Z (GMT). No. of bitstreams: 1 marianagenymoreira.pdf: 8374988 bytes, checksum: 38a7b2c61f3df104e6c9f034df1386ae (MD5) Previous issue date: 2016-05-31 / Nas últimas décadas a qualidade da energia elétrica disponibilizada na rede elétrica tornou-se foco. Este fato é justificado pela combinação dos aumentos da poluição dos sinais na rede e do número de dispositivos eletrônicos sensíveis às variações do sinal de alimentação, especialmente tendo em vista o novo cenário de redes inteligentes. Um dos desafios das redes inteligentes é a redução de eventos ou falhas devido à baixa qualidade de energia elétrica, principalmente envolvendo distúrbios harmônicos e inter-harmônicos, provocados pela utilização de cargas e sistemas eletrônicos. Os impactos e prejuízos causados por distúrbios harmônicos e inter-harmônicos são importantes o suficiente para torná-los foco de inúmeros estudos, posto que não há, até a presente data, um método de análise desses componentes eficiente o bastante para atuar no controle e proteção de sistemas de potência. Este trabalho busca contribuir para a melhoria da análise desses componentes de frequência e, nesse sentido, propõe um sistema de detecção, classificação e identificação de distúrbios de qualidade de energia, especialmente, harmônicos, sub-harmônicos e inter harmônicos, baseado em estatística de ordem superior. São contemplados ainda distúrbios de amplitude de curta duração: sags e swells. A estrutura proposta contempla ainda um contador de componentes inter-harmônicos e sub-harmônicos, capaz de apontar a existência e quantificar esses componentes mesmo quando combinados a outros distúrbios harmônicos. As metodologias propostas pelo trabalho exibem resultados bastante expressivos tanto em relação à eficiência das aplicações em qualidade de energia quanto em relação ao desempenho computacional. / The power quality available on the electrical power system became focus in the last decades. This fact is explained by the combination of signal pollutions increasing and the number of electronic devices sensitive to power signal variations, especially in the smart grids scenario. One of the challenges of smart grids is the reduction of events or failures due to the low power quality, mainly involving harmonics and inter-harmonics disturbances, caused by the use of fillers and electronic systems. Impacts and losses caused by these disturbances are of great concern in numerous studies, since there is not an efficient analysis method capable of dealing with this kind of disturbances. This thesis seeks to contribute in the sense of harmonics and inter-harmonics analysis by proposing a power quality disturbances detection, classification and identification system, based on higher order statistics. The proposed structure also includes a inter-harmonics and sub-harmonics components counter, able to point out the existence and to quantify these components even when they are combined with other harmonic disturbances. The proposed methodologies show suitable results both in terms of efficiency of investments in power quality as compared to the computational performance.

Landstinget Västernorrland har i dagsläget installerat cirka 2600 kvadratmeter solpaneler på sina sjukhus i länet. Planer finns att utöka detta ytterligare. Eftersom solenergin står för en växande andel av elförsörjningen på dessa sjukhus, så väcks frågan om detta kommer ha någon negativ påverkan på dessa sjukhus elkvalitet.   Syftet med arbetet är undersöka om elkvaliteten i inmatningspunkterna för solcellsanläggningarna ligger inom gränsvärdena specificerade enligt EIFS 2013:1 för allmän distribution, samt om någon negativ på-verkan kan påvisas från solcellernas elproduktion. Resultatet visade att samtliga punkter i föreskriften EIFS 2013:1 för elkvalitet uppfylldes.   Det gick inte att påvisa att produktionen från solcellerna hade någon direkt negativ påverkan på sjukhusets elkvalitet i mätpunkterna som undersöktes. Denna slutsats kunde stödjas av att de psykiatriska avdelningar visade god elkvalitet, trots att den installerade effekten solceller är ungefär dubbelt så stor där som på det centrala sjukhuset.   Montagevinkeln för solpanelerna undersöktes också, och enligt en simulering som utfördes i PVGIS, så visade det sig att den optimala vinkeln för en enskild solpanel på den aktuella breddgraden är 44 grader. Det behövs dock ytterligare undersökningar för att konstatera om denna vinkel är fördelaktig för samtliga anläggningar på sjukhus-området. Rapporten visar också att de 15:e och 8:e relativa övertonerna har mät-värden som ligger relativt nära gällande gränsvärden. För att upprätt-hålla elkvaliteten på sjukhuset under alla förhållanden, så bör en under-sökning genomföras för att lokalisera de största faktorerna till störningskällorna. / The County Council of Västernorrland has as of today, installed around 2600 square meters of solar panels on their hospitals. There are already plans in place to expand this even further in the future. With ever in-creasing share of their total energy usage being supplied from solar power, the question arises if this will have any negative impact on the electrical power quality at these hospitals.   The purpose of this study is to determine if the electrical power quality is currently within the limits defined by the Swedish regulation EIFS 2013:1, and if the production of electrical power from these smaller photovoltaic plants have any negative effect on the power quality at the measured grid feed-ins. The results showed that the power quality on all measured points passed the requirements for the regulation EIFS 2013:1.   Also, no clear evidence of any negative side effects on the power quality, caused by electrical power production from the solar panels could be determined. This was supported by the measured power quality being better at the psychiatric departments, despite the installed nameplate capacity being about twice as high as on the main hospital building.   The mounting angle of around 15 degrees was found not to be optimal for a single solar panel at the latitude where the installations are located. A simulation ran found the optimal angle to be 44 degrees. Despite this, more investigations are needed to determine if a higher angle is advantageous to all the installations on the investigated hospital area. Lastly, the report showed some reason to be concerned about the 15th and 8th relative harmonics, as they both had measured values being close to the regulation limits. In order to improve power quality in the future, and avoid exceeding regulation limits, it is therefore recommended that an investigation is performed to determine the largest sources of 15th and 8th relative harmonics.

O presente trabalho tem como objetivo comparar o desempenho de diferentes metaheurísticas bio-inspiradas aplicadas à resolução de problemas de otimização multiobjetivo do controle de tensão e reativos, ou controle Volt/VAr, em redes elétricas inteligentes. Entre os algoritmos implementados estão o algoritmo genético, o algoritmo memético, a otimização por colônia de formigas, a otimização por enxame de partículas e o strength pareto evolutionary algorithm (SPEA2). Aplicações dos algoritmos à resolução de problemas de otimização do controle Volt/VAr, em redes de distribuição de energia elétrica com dimensões reais, são utilizadas para comparação de seus indicadores de desempenho. A avaliação é feita tanto em relação à velocidade de busca quanto em relação à qualidade da solução encontrada. Os algoritmos mostraram resultados promissores para aplicação a redes de distribuição com dimensões reais, encontrando soluções de qualidade em tempos de busca aceitáveis. Parte deste desempenho se dá pelos métodos meta-heurísticos, parte por conta da modelagem adotada no processo de otimização. / The present work aims at comparing the performance of different bio-inspired metaheuristics applied to the Volt/VAr control multiobjective optimization problem in smart grids. Among the algorithms implemented are the genetic algorithm, the memetic algorithm, ant colony optimization, particle swarm optimization and the strength pareto evolutionary algorithm (SPEA2). Applications of the algorithms to solve Volt/VAr control optimization problems in distribution networks with real dimensions are used to compare their performance indicators. The evaluation is done both in relation to the search speed and in relation to the quality of the solution found. The promising results show that the algorithms are applicable to distribution networks with real dimensions, finding quality solutions in acceptable search times. This performance is obtained due to both the metaheuristic methods, and the modeling adopted in the optimization process.

In this report, studies on interharmonics from three different measurement sites are performed. The first site is a wind park with three turbines, where the measurements are performed at the point of common coupling of these three. The second site is a network which consists of a PV inverter and two types of EV chargers – a DC charger or an AC charger. Measurements are performed with three different set-ups in this site – only AC charger connected, only DC charger connected, and AC charger and PV inverter connected simultaneously. The third site where measurements were made is a microgrid using frequency control in order to signal how the microgrid should operate at the moment. The interharmonic analysis was conducted using desynchronized processing technique (DP) and Sliding-Window Estimation of Signal Parameters via Rotational Invariance Techniques (SlidingWindow ESPRIT or SWESPRIT). The result from the wind park is that closely and evenly spaced interharmonics can be seen when the current suddenly increases (could be fast variations in wind speed). It is however uncertain if these interharmonics are caused by spectral leakage or not since SWESPRIT estimates the fundamental frequency to vary drastically when wind speed varies. It is observed that the SWESPRIT estimation of fundamental frequency could be caused by sudden changes in phase angle as the current varies. Further investigation and analysis are needed. The result from the measurements on the site with EV chargers and a PV inverter is that eight distinct patterns can be observed. Some patterns appear to come from the upstream grid, while some appear to be caused by either one of the EV chargers or the PV inverter, or interaction between them. Further studies are needed. The result from the microgrid measurements is that two distinct patterns at high frequencies (above 1000 Hz) can be observed during grid connected mode and island mode, respectively. During transitions between grid connection and island mode or vice versa, the fundamental frequency varies drastically, and it is therefore hard to analyse potential interharmonics and draw inferences. Further studies are needed. Advantages and disadvantages, as well as ideas for improvements, of the two applied signal processing methods are discussed throughout the different case-studies.

The diploma thesis deals with the parameters of electricity quality. The aim of this work is to design and implement a prototype device that will allow remote measurement of power quality. The proposed system uses NB-IoT technology for data transmission. The system enables remote measurement of important parameters of electrical energy, such as the magnitude of the supply voltage or the frequency of the electric network. The device can measure electric current, average voltage values and detect dip / swell voltage events. The device reads a sampled electrical signal suitable for harmonic analysis. The device has started to meet the requirements for measuring device of class S according to EN 61000-3-40.

The thesis focuses on the power management support of battery systems in charging mode and charging systems for electric vehicles in the LV network. The thesis includes an overview of the distribution network of the Czech Republic, means of voltage regulation and the existing legislative framework for the connection of charging systems. The thesis describes the methods of active and reactive power control depending on the voltage and frequency. The practical part focuses on the simulation of grid support at different penetration levels of BESS and EVC in MATLAB Simulink and the verification of the support function on a laboratory system. In the last part, the methods of implementing the control system for BESS and EVC operating in the LV grid are specified.

This thesis is about reactive power compensation in industrial network. Task is design reactive power compensation devices, so that the power factor, which is main indicator of power quality, was within the limits required by the distributor. This is applied to wholesale customers of electrical energy. Reactive power consumed by appliances increased the current that flows through the network, transmission losses and voltage drop. Reactive power compensation is a measure reducing load current and ohmic losses in a supply line. Given that the compensation is one of the significant cost-saving measures in electric power distribution. Distributor requires electric power consumption with a lagging power factor in the range from 0,95 to 1. Other values of power factor are penalized.

This thesis deals with power quality and load modeling. The issues of power quality, principles of load model creation and various types of loads and their principles are described and explained in this thesis. Various software and its main adventages in power systems modeling are described and various load models and simulations in PSCAD program are created and described at last.

This diploma thesis deals with elektrical power quality in DC grids. Electrical power is commodity and therefore it must be represented not just with quantitative, but also with qualitative parameters. Nowadays, there is an increasing demand for bigger implementation of renewable energy sources and more efficient power systems, which motivates installation of DC grids. However, development of DC grids is decelerated by lack of standardization alson in power quality. The work includes definition of power quality parameters and their measurement methodology.

Power Quality (PQ) has gained a lot of importance in the last decade. Several solutions to power quality problems have been proposed and developed. With the advent of solid state technology and power electronics in the power system protection devices, faster switching is achievable. In order to control and minimize the power quality problems which occur in extremely short times of less than 100ms, the need arises for a selection of devices that can switch faster than today. Also, the economic losses that occur in the network due to the power quality problems increase the incentive to transform the existing devices into faster and e fficient devices. This transformation can be seen as valuable from both a technical and economical point of view to the distribution networks today where a large number of customers are connected. However, in order to interpret the value these fast switching devices render to the distribution network a prior study is required. This thesis presents a picture of the devices that can be suitable for fast switching in today’s distribution network, and how to determine their value to the distribution network. Further it summarizes the research work related to this field. The description of the devices and technical aspects is presented first. A literature review of proposed devices is given. The technical aspects of power quality and its problems is described. An approach to estimate the value of the fast switching devices is detailed from different literature. The study shows that fast switching devices can be worthy to invest in when seen from a distribution network’s perspective provided that different technical aspects are taken into account.